Different subtypes of wasteosomes in the human hippocampus

Treballs Finals de Grau de Farmàcia, Facultat de Farmàcia i Ciències de l'Alimentació, Universitat de Barcelona, 2022. Tutor/a: Jordi Vilaplana, Marta RibaWasteosomes (also known as corpora amylacea) are polyglucosan bodies that amass waste substances. They are generated in the central nervous system during normal aging and neurodegenerative processes, then extruded into the cerebrospinal fluid and finally phagocytised by macrophages in the cervical lymph nodes. In this work we study the possible existence of different wasteosomes depending on their location in the human hippocampus. We performed staining techniques combined with digestion with γ-amylase. These techniques were Lugol’s iodine, periodic acid-Schiff and concanavalin A staining, and a double indirect immunofluorescence to detect the neo-epitopes and the protein p62. Results showed there are two subtypes of wasteosomes with respect to their behaviour towards γ-amylase and their content in neo-epitopes and protein p62. Wasteosomes in the inner areas of the hippocampus contained more protein p62, less neo-epitopes, and had a less resistant polymerised structure towards γ-amylase. Conversely, wasteosomes in the peripheral areas of the hippocampus contained less protein p62, more neo-epitopes, and had a more resistant polymerised structure towards γ-amylase. The differences observed could be related to different maturation stages. Wasteosomes in the inner areas could have a less phosphorylated and a more branched amylopectin-like polymer structure, whereas wasteosomes in the peripheral areas could have a mainly phosphorylated and a less branched amylose-like polymer structure. These findings reinforce that wasteosomes are involved in the elimination of brain waste substances, for which reason they undergo a maturation process during which composition and structural changes may occur. Key words: corpora amylacea, wasteosomes, γ-amylase, human hippocampus

Uncovering tau in wasteosomes (corpora amylacea) of Alzheimer's disease patients

Brain corpora amylacea, recently renamed as wasteosomes, are polyglucosan bodies that appear during aging and some neurodegenerative conditions. They collect waste substances and are part of a brain cleaning mechanism. For decades, studies on their composition have produced inconsistent results and the presence of tau protein in them has been controversial. In this work, we reanalyzed the presence of this protein in wasteosomes and we pointed out a methodological problem when immunolabeling. It is well known that to detect tau it is necessary to perform an antigen retrieval. However, in the case of wasteosomes, an excessive antigen retrieval with boiling dissolves their polyglucosan structure, releases the entrapped proteins and, thus, prevents their detection. After performing an adequate pre-treatment, with an intermediate time of boiling, we observed that some brain wasteosomes from patients with Alzheimer's disease (AD) contained tau, while we did not detect tau protein in those from non-AD patients. These observations pointed the different composition of wasteosomes depending on the neuropathological condition and reinforce the role of wasteosomes as waste containers

Analyzing the Virchow pioneering report on brain corpora amylacea: shedding light on recurrent controversies

The frst report of corpora amylacea (CA) is attributed to Morgagni, who described them in the prostate in the eighteenth century. Nearly a hundred years later, and following the lead started by Purkinje, Virchow described them in the brain. He made a detailed description of the most useful techniques to visualize them, but he failed to describe the cause of why CA do appear, why they are mainly linked with the elderly, and which is their clinical signifcance. Although in the last two centuries CA have received little attention, recent data have been able to describe that CA accumulate waste products and that some of them can be found in the cerebrospinal fuid and lymphatic nodes, after being released from the brain. Indeed, CA have been renamed to wasteosomes to underline the waste products they gather and to avoid confusion with the term amyloid used by Virchow, now widely related to certain protein deposits found in the brain. Here, after providing a commented English translation of Virchow's fndings, we provide a recent update on these structures and their connection with the glymphatic system insufciency, for which wasteosomes should be considered a hallmark, and how these bodies could serve as diagnostic or prognostic markers of various brain conditions